Monday, April 4, 2011
Tiktaalik
Looking at Your Inner Fish as a whole, Tiktaalik was a fish that lacked an operculum; what does this tell us about the animal? Furthermore, Tiktaalik had a true neck; what did this allow it to do(advantages)? Tiktaalik was not just the "missing link" rather it was the transitional form, analyze this from an evolutionary standpoint and include outside information. -Eryk Fundakowski arthur2446@comcast.net
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The fact that Tiktaalik does not have a true operculum is one of the most important characteristics about this interesting creature. The absence of an operculum affected the organism by “giving” it a neck. Since an operculum is “a series of bones that serve to attach the head to the body”, a creature that has one would have to turn their entire body in order to see their surroundings (Shubin 206). Fish are good examples of organisms that have operculum and are the key to the evolutionary significance of Tiktaalik because after all, Tiktaalik is the link between water and land-based animals. Over millions of years, as the creature began “losing” its operculum, the advantages of a functional neck became clear. A neck is useful “in settings where the body is relatively fixed, as is the case in shallow water and on land where the body is supported by appendages planted against a substrate” (UChicago). Obviously, because of the enhanced movement allowed by the elimination of a true operculum, natural selection favored these organisms and thus, this characteristic became more and more common among the population over time.
ReplyDeletehttp://news.uchicago.edu/article/2008/10/15/fishapod-reveals-origins-head-and-neck-structures-first-land-animals
Matt Micucci (coochqbk@sbcglobal.net)
Tiktaalik, like Matt explained, lacked the series of bones that attach the head to the body in the fish (Shubin 204). Instead, what Tiktaalik had was a real neck! The role of the operculum is to cover and protect the gills while connecting the head to the body, playing a part in the breathing mechanism of fish (http://www.iowas.co.uk/fish%20anatomy.html). While Matt talked about the function of the connecting aspect of the operculum, what is equally important in the evolutionary perspective is the fact that without the operculum, breathing worked differently in Tiktaalik. Although it wasn’t explained in Shubin’s book, an advantage of having a neck, besides being able to move the head independently of the body, is that it is a transition from having gills to not having gills. Opercula are vital in obtaining oxygen for many fish, so without it, the many generations following Tiktaalik naturally being to transform their inner circulatory systems into one which is found in mammals. If the operculum is no longer there to facilitate breathing, there must be another way to do so, therefore after the neck formed, other features, after generations upon generations formed as a result to make acquiring oxygen more simple.
ReplyDeleteFurthermore, to expand on Matt’s point about the neck being advantageous to move around, in Shubin’s book, he said, “A neck is advantageous in settings where the animal is supporting itself on solid ground, as is the case in shallow pools of water, or on land” (206). In other words, because Tiktaalik had arms and was able to crawl around on the bottom of the ocean floor, a neck was advantageous in that situation so it can turn its head, showing that the arms probably came before the neck.
Finally, Matt explained the steps of evolution from the fish with an operculum to Tiktaalik to something further down the evolutionary chain, like us. Although I agree that natural selection would favor an organism with a neck, I am able to build on how this is evolution. The neck, as Matt already explained, is an advantage, and because of this mutation that happened (luckily being successful), this animal was able to survive and reproduce. More organisms with necks were made and they survived and reproduced. Soon, much of the population had necks -- thus, like Matt called it, natural selection. “Natural selection is based on differential success in survival and reproduction” (Campbell 475). Tiktaalik was not the missing link because although he had a neck, he was not necessarily the first organism to have a neck. Plus, just because he had a neck doesn’t mean that that neck is what made the human race. Every single mutation any organism has is the continued transitional form.
-Mchelle Layvant, michellel94@hotmail.com
As Matt previously stated, the absence of operculum is one of the most interesting and important characteristic of Tiktaalik. However, not only does the operculum connect the head and the body of the bony fishes, but it also helps the fish to gain oxygen without movement, as the operculum opens the gills as the fish’s mouth closes so that water can go through the gill, unlike the cartilaginous fishes, who also do not have opercula (http://en.wikipedia.org/wiki/Operculum_(fish)).
ReplyDeleteSince Tiktaalik lacked an operculum, they had to swim constantly to breathe, just like the sharks. Or, they probably did not “need” opercula anymore, so they were deformed, since the Tiktaalik developed a primitive shoulder and changed their habitat to shallow waters. Also, we can see that the Tiktaalik, unlike many other bony fishes, have their eyes positioned so that it is more like the reptiles’, where it is more at the top portion of the head, for clearer visuals. However, because of this change of placement in eyes, they would lack the visual field where they could see without turning their body. So, that is probably why the neck was developed, so that the Tiltaalik could turn their head and see more without turning their body. This can be supported with Shubin’s statement saying “A neck is advantageous in settings where the animal is supporting itself on solid ground, as is the case in shallow pools of water, or on land” (206).
Just like how Matt and Michelle said, I believe that the development of the neck gave the Tiktaalik a natural selection, by giving them an advantage for living outside water. Also, I do believe that the Tiktaalik could be the missing link between the bony fishes and the amphibians/reptiles. Of course, there could have been more organisms with similar development as the Tiktaalik underwent. However, if that were the case, then there would be more fossils of organisms similar to the Tiktaalik found before. The lack of numbers of similar species as the Tiktaalik not found either as fossils or living organisms signifies that the Tiktaalik did not reproduce that much despite having an advantage. It is most likely that a mutation occurred rather quickly so that a new species with higher advantage were evolved, while the Tiktaalik did not survive that well. Because of these reasons, I believe they were the missing link between the bony fishes and the amphibians/reptiles instead of being part of the transitional form.
John Park (wisejsm@yahoo.com)
Bosan Menang tidak dibayar ? judi sabung ayam
ReplyDeletemau yang asik ? adu ayam
ReplyDeletetebak gambar ayam sabung berhadiah langsung
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